The present invention relates to novel polymerizable compounds containing at least two acrylate or alkacrylate groups in the molecule, and to a radiation-polymerizable mixture, in particular a photopolymerizable mixture, containing these compounds.
Photopolymerizable mixtures which contain acrylates and/ or methacrylates as polymerizable compounds are known. Photopolymerizable mixtures which, in order to increase the photosensitivity, contain certain combinations of photoinitiators and activators, for example combinations of carbonyl group-containing initiators and tertiary amines, are also known. Such mixtures having a synergistic action are described, for example, in DE-A No. 2,602,419, 2,251,048 and 3,331,157 and in U.S.-A Pat. No. 3,759,807. A disadvantage of these mixtures which contain low-molecular-weight amines is that they have a short shelf life since the amines can easily exude or evaporate, in particular from thin coatings.
In JP-A No. 50/129,214, a photopolymerizable mixture is described which contains a tetra(meth)acrylate of a N,N,N',N'-tetrahydroxyalkylalkylenediamine as a polymerizable compound. The tetrafunctional compound functions as a crosslinking agent.
Mixtures are also known which contain triethanolamine trimethacrylate as a crosslinking agent and are described, for example, in Chem. Abstr. 86 (1977), 30443q and 95 (1981), 220 727n. These compounds also tend to diffuse and evaporate out of the coating on relatively long storage and at elevated ambient temperature.
In U.S. patent application Serial No. 173,936 filed Mar. 28, 1988, high-molecular weight polymerizable acrylates and alkacrylates are proposed which contain at least one amino group and at least one urethane group in the molecule.